1. Field of the Invention
The invention relates to a transport and storage container for liquids, comprising a pallet-shaped support frame of metal or of an electrically conducting plastic material, an exchangeable inner container of plastic material supported on the support frame and being of a single-layer or multi-layer configuration provided with a permanently antistatic outer layer, wherein the inner container is of a parallelepipedal shape or of a cubic shape and has four sidewalls, a bottom, and a top, an upper closable fill socket, and a tapping fixture. The transport and storage container also comprises an outer jacket surrounding the inner container and being comprised of grade bars of metal or sheet metal.
2. Description of the Related Art
The inner plastic container of the transport and storage container of the aforementioned kind for liquids, as disclosed in DE 196 05 890 A1, has a permanently antistatic outer layer which serves together with the metallic support frame as electrical grounding means in order to prevent electrostatic charging of the surface of the inner plastic container by friction of the inner container on the metallic outer jacket during transport. In this way, electrical discharges with spark generation between the inner plastic container and the metal grade jacket, which could result in ignition of flammable materials contained in the transport and storage container and of explosive mixtures of gases and vapors in closed rooms, is to be prevented. However, this exterior grounding by means of a permanently antistatic outer layer of the plastic container cannot dissipate electric charges which are caused during filling and emptying of the inner container and stirring of liquids, for example, for mixing purposes, by friction of liquid on the inner surface of the container and by friction within the liquid itself.
DE 197 31 518 A1 describes a transport and storage container for liquids which is grounded by means of a grade hood of thin metal wire placed onto the inner plastic container or an electrically conducting net or woven fabric applied onto the inner container. With this outer grounding only the electrical charges occurring on the outer surface of the container are dissipated as in the case of the transport and storage container according to DE 196 05 890 A1. Moreover, the electrical grounding of the liquid container by a grade hood, a net or a woven fabric is technically complex and results in a corresponding increase of the manufacturing costs.
In the transport and storage container for liquids disclosed in DE 198 15 082 A1, a grounding member is provided on the tapping fixture mounted on the outlet socket of the inner container. It is embodied as a curved sheet metal or metal plate that extends across a portion of the inner bore of the tapping fixture and is connected by means of a fastening screw and a grounding cable to the support frame of the container. By means of this internal grounding action only in the electrical charges which form within the liquid as a result of liquid friction are dissipated. Moreover, this liquid container entails the danger that upon transport and storage of aggressive liquids the grounding member is damaged by the liquid such that the electrical grounding action is no longer functioning.